Under California law apps designed for use on smartphones and other mobile devices must include a privacy policy that explains what data is gathered and how it is used. Delta was one of a 100 companies who were warned in October that their apps were in violation. They were given 30 days to add a privacy policy to their app.

"Kamala Harris is bringing law and order to the Wild West of the mobile world," said John M. Simpson, Consumer Watchdog's Privacy Project director. "She is serious about privacy and her tough action will mean that California once again leads the nation in protecting consumers' rights."

Harris filed the suit in San Francisco Superior Court Thursday. The suit seeks to enjoin Delta from distributing its app without a privacy policy and penalties of up to $2,500 for each violation.

"Privacy policies don't solve all concerns about protecting privacy," said Simpson. "They do at least inform users how their data is gathered and how it's used. That enables people to make an informed choice about whether to use the app."